Taking CRH2 type axle brake system as prototype, the calculation method of thermal load on axle plate and the determination of boundary conditions were studied based on frictional power method. According to the energy conservation method, the heat flux density applied to the brake disc surface is simplified, and the function curve of average forced convection heat transfer coefficient and average natural convection heat transfer coefficient under train emergency braking condition is determined. In the ANSYS software, the temperature dis- tribution and the stress field of the brake disc in the axle disc are simulated under the emergency braking condi- tion of the CRH2 high speed motor car. The results show that during the braking process, the temperature of the surface of the train brake disk rises rapidly at the moment of starting braking. When reaching a certain peak, the temperature slowly drops until the brake is stopped. Brake thermal stress after the start of a sharp rise, and then gradually reduce the speed with ease release.